Drought threatens Lobau’s rich wildlife habitat

The Lobau, a national park and floodplain landscape on the outskirts of Vienna, is facing severe water shortages despite being one of Austria’s most diverse habitats, according to ORF Vienna. Around one fifth of all plant and animal species found in Austria live there.

“It is like a living museum,” said aquatic ecologist Christian Griebler on the ORF Vienna podcast Stadtwandel. Unlike specimens preserved in drawers or jars, the Lobau’s species can still be protected in their natural environment.

The Lobau is home to about 11,000 animal species, most of them insects. Austria has around 55,000 animal species in total. The area also has a diverse plant life, while about two thirds of Austria’s dragonfly species are found there.

Griebler specialises in groundwater habitats. He described the Lobau as one of the world’s most species rich groundwater environments. Its groundwater contains invertebrates such as amphipods, woodlice and copepods, as well as two threatened snail species listed on the Red List.

Groundwater organisms live in gaps between layers of sediment, which Griebler compared to an aquarium filled with gravel. The water bearing layer is only about five to 20 metres deep and lies above a layer that holds back groundwater, making it vulnerable to outside influences.

The groundwater is used for farmland and forms part of Vienna’s water supply. During periods of high demand, such as heatwaves, or when the high spring water pipelines are being serviced, additional water from the Lobau waterworks is fed into the city’s distribution network.

The waterworks is in the Lower Lobau. While the Upper Lobau can receive water from the New Danube, the Lower Lobau is almost cut off from the Danube because of river regulation and the construction of the Danube Island. Water can enter through the Schönau opening only during floods, bringing sediment that contributes to the area’s silting up.

Separating the groundwater flow causes the groundwater level to fall over time through use, evaporation and other factors, Griebler said. The climate crisis is worsening the problem: the Danube level is lower and water evaporates more quickly. The Lower Lobau almost completely dried out this summer.

The Upper Lobau currently depends on artificial water replenishment, but Griebler said the Lower Lobau also needed to be connected to this supply. Surface water cannot yet be diverted there because of concerns about drinking water, as water from the New Danube does not meet drinking water standards.

Vienna is examining possible measures and is expected to present a result by the end of the year. Griebler said the entire Lobau needed increased water flow and that some channels might have to be dredged to counter silting. In the longer term, he said, the water system would need to be restored with greater natural dynamics. Water treatment could become necessary to protect drinking water quality as temperatures rise.